const int leb_pin = 8;
unsigned long previousMillis = 0;
const unsigned long interval = 2000;

void setup() {
  // put your setup code here, to run once:
  pinMode(leb_pin,OUTPUT);
}

void loop() {
  unsigned long currentMillis = millis();

  if (currentMillis - previousMillis >= interval) {
    previousMillis = currentMillis;

    digitalWrite(leb_pin, !digitalRead(leb_pin));
  }
}